During operation, a conventional vented tumble dryer draws air from the surrounding area, heats it, and directs it into the drying chamber or drum of the dryer. The dryer then exhausts the air and retained water vapor through a channel to the outside. As shown in FIGS. 1-3, a known vented dryer 100 generally includes a rotatable drum 102; an air supply channel 104 which introduces fresh air from within the dryer housing or cabinet 106 into the drum 102 via manifold 204; a heater 202 supplied at air supply channel 104, which heats the air introduced into the air supply channel 104; and an air exhaust channel 108 to exhaust hot air and water vapor from the dryer, typically to the outside of the house or other building in which the dryer is located. A process air fan or blower 110 is provided downstream of the drum 102 for drawing air through the system and out the exhaust channel 108. A lint filter 206 for collecting lint and other debris in the air is placed between the drum 102 and the exhaust channel 108. In such a vented tumble dryer 100, the sole heat source is the heater 202 upstream of the drum 102. Further, heat recovery may take place by a slight warming of the air in cabinet 106 before it is drawn into heater 202, by virtue of the heat in the cabinet 106 generated by continued operation of the dryer 100.
Some dryer systems use partially recirculated air in addition to the conventional heater to improve energy efficiency. These systems mix a portion of the exhaust air with the air being introduced into the drum. For example, commonly owned U.S. patent application Ser. No. 13/437,499, filed on Apr. 2, 2012, and titled “Dryer With Air Recirculation Subassembly,” which is hereby incorporated by reference in its entirety, describes a dryer system using recirculated air to increase efficiency. In these systems, the warm, moisture-laden exhaust air holds the potential to absorb additional molecules of water when recirculated through the dryer, and thus the heat energy of that air can be reutilized to improve operating efficiency.
FIG. 4 illustrates an example vented recirculation dryer 400 with portions of cabinet 406 removed, which redirects at least a portion of exhausted air back to air supply channel 404 and ultimately to drum 402. Specifically, the recirculation dryer 400 is similar to vented dryer 100, except recirculation dryer 400 comprises air recirculation channel 414 connecting air exhaust channel 408 with air supply channel 404. Process air fan or blower 410 pulls air from drum 402 through a conventional lint filter 412. A first portion of this air is exhausted through exhaust channel 408, similar to the operation of exhaust channel 108 of vented dryer 100. However, a second portion of the air is recirculated back to air supply channel 404 via air recirculation channel 414, which is then combined with fresh air entering from cabinet 406 at inlet 416 and ultimately supplied back to drum 402 through air supply channel 404. Accordingly, during operation, air passing through air supply channel 404 (and across a heater within air supply channel 404, not shown) comprises air from cabinet 406 and recirculated air pulled from drum 402. In the right proportions, use of such a combination may increase the overall efficiency of vented dryer 400.
However, one concern with using recirculated air is that the recirculated air may contain lint and debris, even after passing through a conventional lint filter 412. That is, when heated air is pulled across articles in drum 402 by blower or fan 410, it may collect lint or debris from the articles. Although most dryers have a standard lint filter (e.g., lint filter 206 of vented dryer 100 shown in FIG. 2 or lint filter 412 of recirculation dryer 400 shown in FIG. 4) to remove most of this lint, some fine debris may inevitably remain in the exhaust air flow. Recirculating a portion of this exhaust air back toward the heater thus poses the risk that accumulated lint may ignite in the heater and be carried into drum 402.
Some recirculation dryers thus include a recirculation air filter, positioned in the air recirculation channel, to remove particulates left in the recirculated air. However, such filters require periodic cleaning and/or replacement, which can be difficult and require complex systems due to the location of the recirculation air channel. For example, with respect to recirculation dryer 400, a recirculation air filter may be located at the junction between exhaust channel 408 and air recirculation channel 414. But because exhaust channel 408 and air recirculation channel 414 meet in cabinet 406 below drum 402, the recirculation air filter is not readily accessible by a user. Thus, recirculation dryer 400 must be partially disassembled in order to service the recirculation air filter, or, alternatively, internal cleaners must be employed.
As a further example, G.B. Patent Appl. Publ. No. 1,369,713, filed Feb. 23, 1973, and titled “Improvements in or Relating to Direct-Air Tumbler-Driers and Air-Recirculatory Conversion Means Thereof,” describes a recirculation air filter that may be periodically serviced through a service hatch provided in recirculation ductwork. Further, U.S. Pat. No. 8,240,064, filed Nov. 24, 2009, and titled “Dryer with Recirculated Air Proportion and Method for Its Operation,” describes a recirculation air filter that is cleaned internally by internal scrapers and/or internal rinsing agents, or externally (although it is not clear how). Each of these solutions may add considerable cost or complexity to the dryer. Thus, there remains a need for an accessible recirculation air filter in a vented dryer employing air recirculation, which allows a user of the dryer to easily clean and/or replace the recirculation air filter.